A solar module known from DE 198 03 326/U.S. Pat. No. 6,013,870 contains a number of solar cells tandem mounted and series-connected on a common substrate. The module also includes a number of adjacent diodes, also referred to as bypass diodes, likewise tandem mounted and connected in series but antiparallel to the solar cells on the same substrate. The structure consists for example of a glass wafer as the substrate , the front electrode layer deposited thereon, the photovoltaically active layer sequence located thereon, and the subsequently applied back electrodes (See FIG. 3 of DE 198 03 326/U.S. Pat. No. 6,013,870). The substrate and front electrode layer are transparently designed so that sunlight can penetrate into the photovoltaically active layers through said structure in order to produce the necessary mobile electric charge carriers. This is known as a superstrate structure.
The solar module can also be constructed as follows. On the substrate (e.g. a glass wafer) the back electrode layer is first deposited, then the photovoltaically active layer sequence , and subsequently the front electrode layer. In this case sunlight penetrates into the photovoltaically active layers through the last-named layer, which is now transparently designed. This module structure is called a substrate structure
In a module according to DE 198 03 326/U.S. Pat. No. 6,013,870, an electric connection is present between a bypass diode and adjacent solar cell by reason of an electric conductivity (transverse conductivity) of the photovoltaically active layer sequence. Then the front and back electrode layers of the diode and its adjacent solar cell are interconnected by a direct electric contact. Consequently, the electric power of the solar module is reduced. This effect can occur because the photovoltaically active layer is not separated in the area of the separation of the front or back electrode layer in the grooves and of this module.
In the above-described module, the bypass diodes are also not covered upon incidence of light on the side facing the light and thus reduce the power of the solar cell by reason of their opposite polarity to the cell. The produced photocurrent of the solar cell is reduced by the amount of the photocurrent of the bypass diode.